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United States Patent |
6,112,924
|
Zhang
|
September 5, 2000
|
Container with base having cylindrical legs with circular feet
Abstract
A blow-molded container has a central axis, a neck and a cylindrical
sidewall connected with the neck, generally centered about the central
axis and having an end. A generally hemispherical base wall encloses the
end of the sidewall. A plurality of legs extend from and are
circumferentially spaced about the base wall. Each leg has a radially
outermost portion offset inwardly from the sidewall and toward the central
axis. An upper portion of each leg connects the leg with the base wall and
has a radially outermost edge offset toward the central axis with respect
to the sidewall. Preferably, each leg includes a leg sidewall having a
generally cylindrical portion, a first, open end integrally formed with
the base wall and a second end. An end wall encloses the second end of the
leg sidewall and has a generally flat section providing a foot surface
configured to support the container on a surface. Preferably, the leg
sidewall has a closed perimeter extending proximal the open end. A
continuous blend zone portion extends about the closed perimeter of the
leg sidewall and integrally connects the leg with the base wall, the blend
zone portion being generally curved and having a center of curvature
located externally of the container. Further, each leg is preferably
defined in a cross section generally perpendicular to the central axis
that has a shape that is generally either circular or ovular.
Inventors:
|
Zhang; Qiuchen Peter (Wilmington, NC)
|
Assignee:
|
BCB USA, Inc. (Tampa, FL)
|
Appl. No.:
|
150563 |
Filed:
|
September 10, 1998 |
Current U.S. Class: |
215/375; 220/606; 220/608 |
Intern'l Class: |
B65D 001/02; B65D 023/00 |
Field of Search: |
215/373,375,377
220/606,608,609
|
References Cited
U.S. Patent Documents
D269158 | May., 1983 | Gaunt | 215/375.
|
4175670 | Nov., 1979 | Reynolds et al. | 220/606.
|
4313545 | Feb., 1982 | Maeda | 220/606.
|
4318489 | Mar., 1982 | Snyder et al. | 215/1.
|
4380306 | Apr., 1983 | Knopf | 220/606.
|
5320230 | Jun., 1994 | Hsiung et al. | 215/1.
|
5353954 | Oct., 1994 | Steward et al. | 220/608.
|
5484072 | Jan., 1996 | Beck et al. | 215/375.
|
5549210 | Aug., 1996 | Cheng | 215/375.
|
5603423 | Feb., 1997 | Lynn et al. | 215/375.
|
5626228 | May., 1997 | Wiemann et al. | 220/606.
|
5850932 | Dec., 1998 | Beck et al. | 220/608.
|
Foreign Patent Documents |
257588 | Feb., 1990 | JP | 220/606.
|
2067160 | Jul., 1981 | GB | 215/377.
|
Primary Examiner: Weaver; Sue A.
Attorney, Agent or Firm: Wolf, Block, Schorr and Solis-Cohen LLP
Claims
I claim:
1. A blow molded container having a longitudinal central axis, the
container comprising:
a sidewall substantially centered about the central axis and having an end;
a substantially hemispherical base wall enclosing the end of the sidewall;
a plurality of substantially cylindrical legs spaced circumferentially
about and extending from the base wall, the legs having a sidewall and an
upper portion connecting the sidewall with the base wall, the upper
portion having a radially outermost edge which is offset inwardly from the
sidewall toward the central axis, the legs having a substantially flat
circular distal end wall providing a foot surface configured to support
the container on a surface.
2. The container as recited in claim 1, wherein the legs include an open
end which is integrally formed with the base wall.
3. The container as recited in claim 2, wherein the leg sidewall has a
closed perimeter extending proximal the open end and the container further
comprising a continuous blend zone portion extending about the closed
perimeter of the leg sidewall and integrally connecting the legs with the
base wall, the blend zone portion being generally curved and having a
center of curvature located externally of the base.
4. The container as recited in claim 3, wherein the container is formed of
one of polyethylene terephthalate, polyvinyl chloride, nylon, and
polyprylene.
5. The container as recited in claim 4 wherein each leg is defined in a
cross section generally perpendicular to the central axis and has shape
that is generally circular.
6. The container as recited in claim 5, wherein each leg has a portion
disposed more distal from the central axis than the remainder of the leg
and disposed more proximal to the central axis than container the
sidewall.
7. The container as recited in claim 5, further comprising a transitional
zone having a substantial radius that is substantially constant about the
perimeter of each leg end.
8. The container as recited in claim 5, further comprising an outer concave
intersection zone forming a continuous portion of the blend zone.
Description
BACKGROUND OF THE INVENTION
The present invention relates to beverage containers, and more
particularly, to self-standing plastic carbonated beverage containers with
bases having legs providing foot surfaces to support the container.
Plastic containers, particularly blow-molded plastic containers for storing
pressurized liquids, have assumed increasing importance in the beverage
container market. Plastic containers have the advantage of being light
weight, relatively inexpensive to produce, and are more resistant to
breakage and other types of impact damage than are containers made of
metal, ceramics or glass.
Typically, plastic containers are manufactured using a process primarily
comprised of two molding operations. In the first step, a parison or
preform is formed in an injection mold using standard molding techniques.
During the injection molding process, liquefied plastic material is
inserted into the mold and contacts the inner mold surfaces that are
cooled by internally circulated water, such that the liquefied material
solidifies into the desired shape of the preform. The resulting preform is
generally tubular-shaped with a circular cross-section and has an open end
and an enclosed end.
As a result of cooling the liquefied material to form the solid preform,
the preform is extracted from the injection mold at a relatively cool
temperature that is unsuitable for the second molding operation.
Therefore, the preform must be heated to at least a minimum temperature
such that preform becomes sufficiently ductile or stretchable to be
blow-molded, as discussed below. The minimum required temperature is
dependent upon the intrinsic viscosity of the preform material, which is a
measure of the material's resistance to being formed or stretched. Thus,
the greater the intrinsic viscosity of the resin, the higher the required
minimum temperature to bring the preform to a state suitable for
blow-molding. Further, the thicker that the preform is made, the higher
the molding temperature should be as it is more difficult to stretch
thicker material.
Ordinarily, the preform is transported through a heated area, such as a
production oven, so that thermal energy is transferred to the preform to
raise it to the desired minimum temperature. The preform is located within
the oven for a period of time sufficient to raise the preform to the
desired molding temperature. Therefore, the preform will be heated for a
longer period of time if the intrinsic viscosity or thickness of the
preform dictates that a higher forming temperature is required. Further, a
thick preform must generally be heated for a relatively longer period of
time, even if to achieve the same temperature as a thinner preform, as the
greater amount of material requires more thermal energy to raise the
temperature of the preform.
After heating to an appropriate temperature, the preform is placed within a
blow mold. The blow mold has an internal cavity defined by wall surfaces
that have been machined to the desired outer dimensions and shape of the
molded container. Compressed air or another suitable pressurized gas is
directed or "blown" into the hollow center of the preform such that the
preform material stretches both radially outwardly and axially downwardly
into contact with the mold surfaces. As the mold walls are cooled by
internally circulating water, the heated material of the preform
solidifies into a final shape provided by the mold walls substantially
immediately upon contact with the walls.
Often, plastic containers are formed on a variation of the molding process
called "stretch-blow molding". Stretch-blow molding is essentially the
same basic process described above with the additional feature that a
stretch rod is inserted through the center of the preform immediately
before or after or simultaneous with the injection of the pressurized gas.
The movement of the stretch rod facilitates the downward stretching of the
preform toward the lower end of the blow mold.
In particular, the molding of the container base introduces several
limitations into the manufacturing process. One limitation is that the
larger the desired diameter of the finished base, the greater the gas
pressure required to force the material to expand outwardly to reach the
mold surfaces when the gas flow rate remains constant. However, the higher
the pressure used to form the container, the greater the chance the force
of the pressurized gas will cause a rupture in the container material, a
situation referred to in the container-forming art as "blow-through".
Blow-through tends to occur most often in the outer sections of the
container base as the material is stretched further than at other sections
of the container. Therefore, the higher the molding pressure used to form
the container, the greater the required minimum thickness of the preform
to prevent "blow-through" from occurring.
Further, as mentioned above, the greater the thickness of the preform used
to make a given container, the higher that the molding temperature of the
preform should be to enable the preform to stretch sufficiently during
blow molding. The ability of the preform to stretch is most critical for
forming the outer, lowermost portions of a container base as the preform
must stretch the furthest distances both axially and radially to reach the
mold surfaces that form these container portions. Another limitation is
that, given only a specified amount of time for heating the preform, when
the thickness of the preform is increased, the intrinsic viscosity of the
preform material may be limited to below a maximum value so that the
preform remains sufficiently stretchable to form the container. Thus,
certain polymeric resins having a higher intrinsic viscosity may be
unusable for making a container with a greater finished thickness or in a
more time critical process.
Each of the above-discussed limitations to the container forming process
affects what is referred to as the "process window", which is a set of
process parameters that must be carefully controlled in order to produce
commercially acceptable containers on a reliable basis. The factors
included in the process window include the molding temperature of the
preform, material viscosity, dwell time in the mold, pressure of the
air/gas blown into the preform and, in stretch blow-molding operations,
the stretch force of the rod exerted on the preform during the
blow-molding process. Controlling the process window is critical for
efficient manufacturing of the containers as the containers are produced
in a high speed environment such that slight variations, minor
modifications or aberrant fluctuations in any one of these parameters may
lead to the fabrication of containers that are unacceptable.
When the specific configuration of the container is such that the range of
acceptable values for any of the process parameters is decreased (e.g., by
increasing the required molding temperature of the preform), the more
critical it becomes to control these parameters, leading to a situation
called a "narrow process window". With a narrow process window, there is
little allowance for even slight changes to any of the process parameters.
Therefore, the container-forming industry is constantly seeking new ways
to "widen" the process window so as to increase the rate of production of
acceptable containers.
Numerous types of known plastic containers, particularly for use in
containing liquids at elevated pressures, are produced using the
blow-molding process generally described above. These containers are
generally of either two-piece construction, in which a separate base is
attached to the remainder of the container, or a one-piece construction
having an integral base structure. Referring to FIG. 1, a typical
two-piece container 1 has a main container body 2 for holding the intended
contents of the container 1 and a separate base member or cup 3 which is
attached to the lower end of the main body 2 to enable the container body
2 to be supported in an upright position on a surface S. Each component 2,
3 of the container 1 is molded in a separate process and then the two
components 2,3 are assembled together in a third, subsequent process,
generally by gluing the base cup 3 to the container body 2. Typically, the
container body 2 is transparent and made of polyethylene terephthalate
("PET") and the base cup 3 is formed of opaque high density polyethylene
(HDPE).
Generally, the one-piece plastic container with an integral base is
preferable as it requires less material and less processing to
manufacture. Examples of one-piece plastic containers are found in U.S.
Pat. No. 5,320,230 to Hsiung entitled "Base Configuration for Biaxial
Stretched Blow-Molded PET Containers"; U.S. Pat. No. 5,353,954 to Steward
et al. entitled "Large Radius Footed Container"; U.S. Pat. No. 5,484,072
to Beck et al. entitled "Self-standing Polyester Containers for Carbonated
Beverages"; U.S. Pat. No. 5,549,210 to Cheng entitled "Wide Stance Footed
Bottle with Radially Non-Uniform Circumference Footprint"; and U.S. Pat.
No. 5,603,423 to Lynn et al. entitled "Plastic Container for Carbonated
Beverages".
Referring now to FIGS. 2-4, a common type of one-piece plastic container 10
has a base 14 generally adapted from the base cup 3 of the two-piece
container shown in FIG. 1. As best shown in FIG. 4, the base 14 has a
cross-section formed generally as a barrel with an annular ring so as to
be self-standing. One problem with the base structure is that the concave
central portion 19 of the base 14 has the tendency to deflect or "pop"
outwardly by the pressure of carbonation gas when the container 10 is
filled with a substance such as a carbonated beverage. To prevent the
outward deflection of the central portion 19, reinforcing ribs 24 were
added to the base structure such that the base 14 is divided into several
individual legs 16. The resulting base structure is commonly referred to
as "petaloid" (i.e., resembling the petals of a flower).
More specifically, such petaloid bases 14 are typically formed of three or
more legs 16 extending downwardly from the sidewall 12 that forms the main
portion of the container 10. Each leg 16 is multi-sided or multi-faced and
is formed of an outer side wall 17 extending generally continuously from
the container side wall 12, an inner side wall 18 connected with a central
portion 19 of the base 14 and two radially-extending and converging side
walls 20A, 20B. An end wall 22 encloses the lower ends of the four side
walls 17, 18, 20A and 20B and provides a foot surface 21 so that the
container 10 may be placed in a "standing" position upon a surface S.
Further, as discussed above, each adjacent pair of legs 16 is separated by
a rib 24, such that the base 14 has a number of ribs equal to the number
of legs 16. Each rib 24 extends between the side wall 12 and the central
base portion 19 and has a generally arcuate shape.
By having legs 16 formed of a four distinct side walls and a separate
enclosing end wall, regions of high stress concentration are formed. In
particular, high stress concentration occurs in the base sections located
at each inner corner of the legs 16, designated as region "I" in FIG. 3.
The region I encompasses the intersection of four leg surfaces: the inner
wall 18, one of the side walls 20A, 20B, the central base portion 19 and
the proximal rib 24. Although this region, as with the central region 19,
tends to have less biaxial orientation than other portions of the
container 10 since less stretching of the preform occurs in this region
during the molding process, the relatively high rate of stress failure of
containers 10 in this area is primarily due to the geometric stress
concentration arising from the intersections of the several surfaces. When
the container 10 is filled with a pressurized substance, the walls of the
legs 16, the ribs 24, and the central portion 19, deflect outwardly
further at their respective central regions than at the relatively stiff
regions of intersection with the various other wall portions. The
deflection of these various wall portions cause sheer stress to be
concentrated at the regions of intersection between the walls (in a manner
analogous to a bending cantilever), which effect is multiplied by the
convergence of several lines of intersection.
The base region I, as described above, is the area of the container 10 that
is most likely to experience a failure mechanism referred to as
"environmental stress cracking". Environmental stress cracking is the most
common and most serious mode of failure for containers constructed of PET,
such as the containers 10. Due to the stress concentration in region I
arising from the structure of the legs 16 (as described above), the
resulting magnitude of the stress experienced in this region of each leg
16 causes, over a period of several days or weeks, a gradual breakdown of
the molecular structure of the PET material in the region I, initially
causing one or more microscopic openings to form in the region I. Once an
opening is formed, the stress concentration is further magnified at the
opening such that the opening becomes greatly enlarged, leading to a
catastrophic failure of the container 10.
A failure of a container 10 due to environmental stress cracking ordinarily
occurs after a period of at least several days after the container 10 is
filled with a pressurized substance, such as a carbonated soft drink.
Therefore, the failure of the container 10 not only results in a loss of
the container 10, but also a loss of the pressurized contents.
Particularly when the contents of the container 10 is a quantity of a
carbonated soft drink and the failed container 10 is stored with numerous
other containers 10, the resulting spillage of the contents leads to a
relatively labor intensive cleaning process to remove the spilled contents
from the surrounding area.
Ordinarily, PET material is characteristically tough and durable such that
failure of the containers 10 due to environmental stress cracking would
generally not occur without the stress concentration introduced by the
multi-sided structure of the legs 16. Environmental stress cracking is
most likely to occur when the containers 10 are stored under conditions
that are not optimal. Ideally, the containers 10 should be stored with the
lowest feasible carbonation pressure and at the lowest temperature
possible to minimize carbonation pressure. Clearly, by having a lower
pressure, the stress in the walls of the container 10, such as in region
I, will be minimized. Further, the containers 10 should be free of the
lubricants that are used to facilitate handling of the containers 10
during the container-filling process. These lubricants, which are
typically liberally applied to the containers 10 so as to have maximum
effectiveness during the handling operations, contain chemicals which can
cause PET material to break-down.
In reality, however, the ideal conditions are not generally attainable for
the following reasons. Consumers prefer higher levels of carbonation in
the beverages that they drink. Also, it is generally impossible or at
least economically unfeasible to control the temperature of storage areas,
such as warehouses or trailer trucks. Further, processes for removing the
lubricants from the containers 10 are generally too costly to be
implemented, such that the containers 10 are typically stored with a
certain amount of the lubricant coating the base 14. Therefore, due to the
presence of these factors, the resulting environmental stress cracking has
led to an unacceptable number of failures of the prior art containers 10.
One container having a leg configuration that reduces the stress
concentration effect of multi-sided legs is disclosed in U.S. Pat. No.
4,318,489 of Snyder et al. ("Snyder"). As shown in FIGS. 5-7, the Snyder
container 110 has a base 114 formed of a plurality of bulbous or
"spherical" legs 116 extending downwardly from a generally hemispherical
base portion 114. Each leg 116 has a radially outermost wall portion 116a
that is generally "vertically aligned" with the side wall 112 of the
container 110 and the remaining upper end of each leg 116 intersects with
the hemispherical portion 115, as best shown in FIGS. 6 and 7. Although
the Snyder container 110 eliminates the multi-sided leg structure to
thereby reduce stress concentration in the base region I (as described
above), the configuration of base 114 introduces other deficiencies, as
described below, that are not present in the typical container 10.
By having legs 116 that are bulbous or spherically-shaped, each leg 116 has
only a relatively small foot surface 121. Therefore, when the Snyder
container 110 is placed on a surface S, the container 110 is essentially
supported on a plurality of points (i.e., the apexes of the surfaces 121)
such that friction between the container 110 and the surface S is
substantially less than with the common petaloid container 10. The minimal
friction increases the likelihood that the container 110 will either tip
over or slide rather than remain stationary relative to the surface S when
subjected to an external force, which is particularly problematic for the
handling of numerous empty containers 110, such as when the container 110
is located upon a tabletop conveyor (not shown) during a "bottling" or
other container-filling operation.
Furthermore, as each foot surface 121 is located at approximately the
center of the respective leg 116, the legs 116 should be located as far
from the central axis 111 of the container 110 as possible so that the
container 110 has a sufficient standing ring R. In general, the greater
the standing ring of any container, the greater the container's stability
and the less likely the container is to tip over during handling. This is
due to the individual foot surfaces (e.g., 121) of the container being
located further from the container's center of mass (which is located on
the central axis 111), and thus each having a longer lever arm with which
to resist a "tipping" moment arising from a force applied to the
container. Therefore, the structure of the legs 116 having foot surfaces
121 only at about the middle thereof dictates that the legs 116 should
located with the outermost edges 116a of each leg 116 vertically aligned
with the side wall 112 of the container 110 for purposes of stability.
Another serious limitation of the Snyder container 110 results from the
configuration of the legs 116 having an outer edge 116a "vertically
aligned" with the side wall 112. By being "vertically aligned", the outer
edge 116a of each leg 116 is thus located at the maximum distance from the
center line 111 of the container 110. Therefore, when forming the legs
116, the preform material has to stretch to both the maximum radial and
axial distances of the container 110, thereby causing the material in this
region to thin to the extent that blow-through is likely to occur.
Increasing the thickness of the preform to alleviate the excessive
thinning necessitates increasing the pressure of the injected air so that
the preform material stretches a sufficient distance to form the
vertically-aligned outer edge 116 of each leg 116. However, the increased
air pressure itself will likely cause blow through to occur. Therefore,
the Snyder container 110 is only potentially produceable in a smaller
size, such as of the now common "twenty-ounce" variety.
Furthermore, a problem that is common to both types of prior art containers
10, 110 described above is that, during formation of the container base
14, 114, the material forming the lower, outer edges of the legs 16, 116
(indicated in the drawings as region "O") undergoes greater stretching
than at any other section of the container 10. This is due to the preform
material in these regions having to be stretched both the greatest axial
distance (as with the bottom surface of the base 14, 114 generally) and to
stretch almost the same radial distance as the sidewall 12, 112. Due to
the substantial amount of stretching of the material, if the preform is
not sufficiently thick, the region O of each leg 16, 116 tends to become
over-stretched and form an opaque section of material referred to as
"pearled". Pearled areas are extremely thin and become easily wrinkled or
dented, either outwardly from the internal pressure of the pressurized
substance or inwardly from impact to the container (e.g., from being
dropped). Further, pearled areas diminish the aesthetic appeal of the
container 10, 110 to a consumer as there is the general expectation,
particularly with carbonated beverage applications, that the walls should
be generally transparent as with the glass containers that PET containers
have replaced.
To eliminate the occurrence of pearling in the outer areas of the legs 16,
116, the thickness of the preform may be increased, with a corresponding
increase in material costs. Another way to minimize the occurrence of
pearling is to heat the preform for a longer period of time to increase
the molding temperature so that the preform material is more ductile and
thus less likely to over-stretch. The increase in heating time results in
a reduced process window such that the rate of production of the
containers 10, 110 is decreased.
From the foregoing, it will be appreciated that it would be desirable to
have a container with an improved base that minimizes the amount of
material necessary to manufacture each container. Further, it would be
advantageous to provide a container having a design that is resistant to
environmental stress cracking. It would also be desirable to provide a
container having a sufficiently large foot surface area and/or standing
ring so that the container has maximum stability to prevent toppling of
the container, particularly during the manufacturing thereof. Furthermore,
it would be desirable to provide a container with an improved base
configuration such that the process window for manufacturing the container
is maximized.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a blow-molded container having a
central axis and comprising a sidewall generally centered about the
central axis and having an end. A base wall encloses the end of the
sidewall. At least one leg extends from the base wall and has a radially
outermost portion offset inwardly from the sidewall and toward the central
axis.
In another aspect, the present invention is a blow-molded container having
a central axis and comprising a sidewall generally centered about the
central axis and having an end. A base wall encloses the end of the
sidewall. At least one generally cylindrical leg extends from the base
wall and has an upper portion connecting the leg with the base wall. The
upper portion of the leg has a radially outermost edge offset toward the
central axis with respect to the sidewall.
In yet another aspect, the present invention is a container comprising a
sidewall having a central axis and at least one end, the sidewall being
generally centered about the central axis. A base includes a hemispherical
portion integrally formed with and enclosing the end of the sidewall. A
plurality of legs extend from and are spaced circumferentially about the
hemispherical portion. Each leg has a portion disposed more distal from
the central axis than the remainder of the leg and disposed more proximal
to the central axis than all portions of the sidewall.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The foregoing summary, as well as the detailed description of the preferred
embodiments of the invention, will be better understood when read in
conjunction with the appended drawings. For the purpose of illustrating
the invention, there is shown in the drawings, which are diagrammatic,
embodiments which are presently preferred. It should be understood,
however, that the invention is not limited to the precise arrangements and
instrumentalities shown. In the drawings:
FIG. 1 is a side elevational view in cross-section of a two-piece prior art
container;
FIG. 2 is a partially broken-away, elevational view of a prior art
one-piece plastic container showing the integral base portion thereof;
FIG. 3 is a bottom plan view of the first prior art container;
FIG. 4 is a partially broken-away side cross-sectional view of the first
prior art container taken through line IV--IV of FIG. 3;
FIG. 5 is a partially broken-away elevational view of a second type of
prior art container having an integral base;
FIG. 6 is a bottom plan view of the second prior art plastic container;
FIG. 7 is a partially broken-away side cross-sectional view of the second
prior art container taken through line VII--VII of FIG. 6;
FIG. 8 is a side elevational view of an improved container in accordance
with the present invention;
FIG. 9 is a partially broken-away, bottom perspective view of the improved
container;
FIG. 10 is a bottom plan view of the improved container;
FIG. 11 is a partially broken-away, side cross-sectional view of the
improved container taken through line XI--XI of FIG. 10;
FIG. 12 is a greatly enlarged view of section XII indicated in FIG. 11;
FIG. 13 is a greatly enlarged, diagrammatic cross-sectional view showing
the joining of a base leg to a typical container sidewall;
FIG. 14 is a side elevational view of an improved container in accordance
with a second embodiment of the present invention; and
FIG. 15 is a partially broken-away bottom perspective view of the
alternative embodiment improved container.
DETAILED DESCRIPTION OF THE INVENTION
Certain terminology is used and the following description for convenience
only and is not limiting. The words "right", "left", "lower", "upper",
"upward", "down" and "downward" designate directions in the drawings to
which reference is made. The words "front", "frontward", "rear" and
"rearward" refer to directions toward and away from, respectively, either
a designated front section of an improved container or a specific portion
of the container, the particular meaning intended being readily apparent
from the context of the description. The words "inner", "inward", "outer"
and "outward" refer to directions toward and away from, respectively, the
geometric center of either the container or a portion thereof as will be
apparent from the context of the description. The terminology includes the
words above specifically mentioned, derivatives thereof, and words of
similar import.
Furthermore, the term "radially outermost" as used herein refers to the
section of a component of the container, and specifically the section of
each leg, that is located the greatest perpendicular distance from the
central axis of the container.
Referring now to the drawings in detail, wherein like numerals are used to
indicate like elements throughout, there is shown in FIGS. 8-12, a first
preferred embodiment of an improved container 210 with a central axis 211.
The container 210 generally comprises an upper neck portion 213, a
generally cylindrical side wall 212 having a first, upper end 212a
extending from the neck 213 and a second, lower end 212b, and a base 214
enclosing the second end 212b of the side wall 212. The base 214 has a
generally hemispherical portion 215 having a first, upper end 215b, formed
integrally with the second end 212b of the side wall 212, and at least one
leg 216, and preferably a plurality of legs 216 extending from and
circumferentially spaced about the hemispherical portion 215.
Each leg 216 has a radially outermost portion 216a that is integrally
joined to the hemispherical portion 215 by an exterior concave region 238.
By being joined to the hemispherical portion 215 by the exterior concave
region 238, the outermost portion 216a of each leg 216 is offset inwardly
with respect to the sidewall 212 such that the radially outermost portion
216a is disposed more proximal to the central axis 211 of the container
210 than is any portion of the side wall 212, resulting in important
benefits as described below. Each of the above-recited elements of the
improved container 210 will be described in further detail below.
Preferably, the improved container 210 is constructed of polyethylene
terephthalate ("PET") as this material due to its inherent flow
characteristics as described in the Background of the Invention section of
this application. However, the improved container 210 may be constructed
of a variety of other plastic resins having satisfactory characteristics,
such as for example, ductility or "stretchability" and intrinsic
viscosity. Such other appropriate materials include, for example, other
saturated polyesters, polyvinyl chloride, nylon and polypropylene. The
present invention is intended to embrace an improved container 210 as
described herein formed of any appropriate polymeric material.
As shown in FIG. 8, the container 210 is preferably a blow-molded beverage
container of the type generally used to contain pressurized substances,
such as, for example, carbonated beverages. Most preferably, the container
210 is constructed as the type of container commonly referred to as a
"2-liter bottle" well known in the carbonated beverage industry and to
ordinary consumers alike. However, it is within the scope of the present
invention to construct the improved container 210 as any other type of
carbonated beverage container, such as, for example, a "1-liter" bottle
used for carbonated beverages. Further, the container may be configured as
any other type of container for any desired pressurized or non-pressurized
liquid, such as, for example, a modification of the known, commercially
available half-gallon plastic milk container.
Still referring to FIG. 8, the improved container 210, as noted above, is
preferably constructed having the elements common to a plastic beverage
container, particularly of the 2-liter variety, except for the structure
of the base 214. More specifically, the neck 213 is generally cylindrical
with a circular cross-section and includes external molded threads 213a
configured to enable attachment of an internally threaded bottle cap (not
shown). Further, the side wall 212 is generally cylindrical with a
circular cross-section and has a diameter substantially greater than the
diameter of the neck 213. Further, the container 210 preferably includes a
generally frusto-conical transition section 225 extending between and
integrally joining the neck 213 to the cylindrical side wall 212. As
described above, the base portion 214 of the container encloses the lower
end 212b of the cylindrical side wall 212.
Although the elements of the improved container 210 common to prior art
containers are constructed as described above and below and depicted in
drawing figures, it is within the scope of the present invention to
construct the improved container 210 in any other appropriate or desired
manner. For example, the side wall 212 may alternatively include
ornamental or even functional ridges (not shown) disposed at the first or
second ends 212a, 212b, respectively, of the sidewall 212. Further, the
side wall 212 may alternatively be shaped, although not preferred, with an
ovular cross-section, a rectangular or square cross-section or in any
other appropriate manner depending on the preferred manufacturing method
for, and/or the common elements of desired application of the improved
container 210. Further, the neck region 213 may alternatively be formed
having another appropriate cross-sectional shape and/or formed without
threads 213a. The present invention is intended to embrace these and any
other alternative configurations and or constructions of the common
elements of the improved container 210 as long as the container 210
includes a base 214 having cylindrical legs 216 as described above and
below.
Referring now to FIGS. 8-12, the base 214 preferably includes a plurality
of cylindrical legs 216, most preferably five cylindrical legs 216,
extending from and integrally joined with the hemispherical portion 215.
The five legs 216 are spaced generally evenly about the circumference of
the base 214 so as to be located generally equidistant from the central
axis 211 of the container 210. However, the base 214 may alternatively be
formed with any number of legs 216 spaced evenly or unevenly thereabout.
As best shown in FIG. 11, each leg 216 has a first, open end 235 integrally
formed with the hemispherical portion 215 of the base 216 and a side wall
230 extending from the first end 235 and having a truncated cylindrical
section 230b and a generally cylindrical portion 230a. Each leg 216
further includes a generally circular end or base wall 232 enclosing the
side wall 230 and having a generally flat section providing an circular
foot surface 221. As described below, the foot surface 221 is configured
to support the container 210 in an upright standing position upon an
external surface S, such as, for example, a household table top or a
working surface of a bottling or other container-filling machine (none
shown).
Referring now to FIGS. 9-11, the end wall 232 of each leg 216 is generally
flat and circular and is integrally joined with the side wall 230 by a
smoothly curved transition zone 233. The transition zone 233 has a
substantial radius R.sub.T that is preferably generally constant about the
perimeter of the end wall 232 such that the transition zone 233 has a
generally uniform annular shape. By having such a transition zone 233
between the side wall 230 and the end wall 232 this section of each leg
216 has no sharp corners or sharp radiuses such that stress concentration
is essentially eliminated therein. Further, the elimination of the sharp
corners in this area of each leg 216 also eliminates the problem of
creasing or wrinkling of the corners, which commonly occurs with
containers 10 having multi-sided legs 16 upon carbonation.
Further, as each foot surface 221 extends across a substantial portion of
the horizontal cross-sectional area of each leg 216, the radially
outermost edge 221a of each foot surface 221 extends proximal to the
radially outermost portion 216a of each leg 216. Therefore, the container
210 has a substantially large standing ring R with a diameter D.sub.R that
approaches or even exceeds the diameter of the standing rings of prior art
containers, such as containers 10 and 110 shown in FIGS. 2-7, even though
the legs 216 themselves are disposed further radially inwardly, and formed
with significantly less material, than the legs (e.g. 16 and 116) of prior
art containers, as discussed in detail below.
Referring again to FIGS. 8-11, each leg 216 is preferably integrally
connected with the hemispherical base wall 215 by a continuous,
inwardly-curved blend zone 236 extending completely about the perimeter of
the first, open end 235 of each leg 216. The term "continuous" as used to
describe the blend zone 236 means extending in a closed, uninterrupted
curvilinear path. Preferably, the continuous blend zone 236 is formed so
as to have at least a minimum outer radius R.sub.B of a substantial
magnitude at all sections thereof such that the blend zone 236 has no
sharp corners or curves. By having both the blend zone 236 at the juncture
between the open end 235 of the leg 216 and the hemispherical base wall
215 and the transition zone 233 (as described above), the container 210
has essentially no stress concentration due to the geometric structure of
the legs 216 and/or the base 214. By eliminating stress concentration in
the legs 216 and the base 214, the container 210 also has the benefit of
significantly higher resistance to environmental stress cracking compared
to prior art containers, such as containers 10 and 110.
Alternatively, although not preferred, the blend zone 236 may be
constructed so as to have a generally sharp radius R.sub.B, having two or
more alternating curved sections so as to form a "rippled" area, and/or
having a generally straight-walled portion connecting the leg 216 to the
hemispherical base portion 215 in the manner analogous to a chamfered
corner (none shown). The present invention is intended to embrace these
and any other alternative configurations for the continuous blend zone 236
as long as the radially outermost portion 216a of each leg 216 is offset
inwardly from the side wall 212 of the container 210, as described above
and in further detail below.
Referring now to FIGS. 11 and 12, as mentioned above, the radially
outermost portion or outer edge 216a of each leg 216 (i.e., located the
greatest perpendicular distance from the central axis 211 as defined
above) is integrally connected with the hemispherical portion 215 of the
base 214 by an outer or exterior concave intersection zone 238. By being
connected with the hemispherical base wall 215 through the concave
intersection zone 238, the outer edge 216a of each leg 216, and thus the
remainder of the leg 216, is inwardly offset from or with respect to the
side wall 212 and toward the central axis 211 of the container 210.
Therefore, the entire leg 216 is disposed more proximal to the central
axis 211 of the container than all portions of the side wall 212.
Preferably, the concave intersection zone 238 forms a continuous portion of
the blend zone 236. Further, the concave intersection zone 238 preferably
has a "vertical profile" (defined herein as the cross-section formed by a
generally vertical section line) constructed as a continuous curve having
a radius or radii R.sub.I with a center(s) (not shown) located externally
of the container 210 and below the upper end 235 of the leg 216, as best
shown in FIG. 12. With such a vertical profile, the concave intersection
zone 238 provides a relatively gradual and smooth transition between the
hemispherical portion 215 of the base 214 and the open end 235 of the leg
216 so as to eliminate any potential for stress concentration in this area
of the container 210. Alternatively, as with the continuous blend zone 236
in general, the concave intersection zone 238 may be formed by two or more
alternating curves so as to create "ripples", by a generally
straight-walled portion, or in any other manner (none shown) as long as
the radially outermost edge 216a of the leg 216 is inwardly offset with
respect to the cylindrical side wall 212 for the reasons discussed below.
By having the above-described concave intersection zone 238 connecting the
radially outermost portion 216a of each leg 216 to the hemispherical base
wall 215, as stated above, each leg 216 is thereby completely or entirely
offset inwardly towards the central axis 211 of the container 210 with
respect to the sidewall 212. Without an intersection zone 238 as
described, the radially outermost portion 216a of each leg 216 would be
connected with the base 214 in one of two manners. Either the outermost
portion 216a would be vertically-aligned with the side wall 212 (FIGS. 4
and 7) with the prior art containers 10, 110, or would be joined by a
concave intersection zone having a radius of curvature centered above the
top of the leg, such that the radially outermost portion would be disposed
further from the central axis 211 than the side wall 212 (i.e., with a
base 214 wider than the side wall 212).
There are several advantages inuring to the improved container 210 by
having a base 214 configured so that each leg 216 is entirely inwardly
offset toward the central axis 211 with respect to the side wall 212. One
advantage is that during the blow-molding of the container 210, the
material in the preform (not shown) is not required to be stretched as far
from the central axis 211 during formation of each leg 216 as compared
with other prior art containers. As a consequence, the material used to
form the legs 216 is much less likely to become over-stretched during the
blow molding process, and thus the occurrence of pearling and blow-through
is significantly reduced. With pearling and blow-through being less likely
to occur, the preform used to form the improved container 210 may be made
of substantially less thickness than the minimum thickness required for
the preforms used to make prior art containers (e.g., 10 and 110).
Therefore, the improved container 210 may be made with significantly less
material than is needed to produce acceptable prior art containers on a
consistent basis. Further, with less stretching of the preform being
required to form the legs 216 (and the base 214 in general), the preform
used to form the container 210 does not need to be heated to as high a
temperature before blow-molding such that the rate of production and the
process window are both increased. For the same reason, resins with a
higher intrinsic viscosity (and thus less ductile) may be used to form the
improved container 210 than would be feasible with prior art containers,
further increasing the process window.
Another advantage to having legs 216 located inwardly from the side wall
212 of the container 210 is that the overall surface area and volume of
each leg 216, and thus the amount of material necessary to form the leg
216, is significantly reduced compared to the legs (e.g., 16 and 116) of
prior art containers. This reduction in leg surface area/volume by the
inward placement of the legs 216 is due to several factors as described
below.
First, one reason the legs require less material than the legs of prior art
containers 10, 110 derives from the fact that essentially all blow-molded
containers, such as for example the prior art containers 10, 110, have a
hemispherically-shaped end wall or portion 15, even when the structure of
the legs (e.g., 16 and 116) is such that the hemispherical portion 15 is
reduced to only the rib portions 24, 124 between the legs 16, 116 and the
central base portion 19, 119, as shown in FIGS. 2 and 5. Thus, the further
toward the central axis 211 that the leg 216 is located, the less minimum
overall height is required for each leg 216 to "bridge" the distance
between the hemispherical portion 215 and a surface S. This is due to the
fact that, as the radial distance from the central axis 11 of a container
10 increases, the further that the hemispherical portion 15 of the base 14
curves upwardly.
Thus, the legs 16, 116 of the prior art containers 10, 110, being
positioned radially outwardly further than the legs 216 of the improved
container 210, are required to be made with a greater height and thus
require more material than the legs 216 of the improved container 210.
Therefore, the preform used to make the improved container 210 may be made
thinner, and with less material, than the preforms used to make the prior
art containers for this reason also.
Further, with the prior art containers 10 having multi-sided legs 16
disposed near the outer perimeter of the container 10, the outer wall 17
of the leg 16 extends into or is blended with the sidewall 12. As best
shown in FIGS. 2 and 3, the outer wall 17 of each leg 16 has a width
W.sub.O, particularly at the upper end 17a, that extends across a
significant portion of the circumference of the sidewall 12. Thus, the
multi-sided legs 16 necessarily have a greater surface area so as to blend
into or with the sidewall 12. As the legs 216 of the improved container
210 are inwardly offset and do not blend with the sidewall 212, the legs
216 are constructed with a smaller, generally uniform cross-sectional
width, and thereby require less material to be formed, than the containers
10 with multi-sided legs 16 for this reason also.
Referring now to FIGS. 9-11, another advantage of the improved container
210 is that the legs 216 each have significantly larger foot surface 221
than that of the prior art container 10 and which far exceeds the foot
surface 121 of the Snyder container 110. By having the substantially
larger foot surface 221, the frictional force between each leg 216 and a
surface S is much greater, enabling the improved container 210 to
withstand greater applied forces without falling over or sliding upon a
surface S. The increased frictional force, and thus increased stability of
the container 210, is particularly critical when the container 210 is
located on a tabletop conveyor during a "bottling" or filling operation as
sliding or toppling of the containers, such as caused by a collision with
another container, may halt or disrupt the bottling operation. When empty,
the containers 210, as with the other containers 10, 110, have relatively
little weight with which to generate friction with a surface S, and thus
the increased friction due to the larger foot surface 221 is a significant
advantage to the improved container 210. This advantage is particularly
acute when compared to the generally bulbous or spherical legs 116 of the
Snyder container 110, which has essentially point contact between each
foot 121 and a surface S.
Referring now to FIGS. 14 and 15, there is depicted an alternative
construction of the improved container 310. The alternative construction
310 is substantially identical to the first preferred construction of the
container 210, except that the base 314 includes six legs 316
circumferentially spaced about the hemispherical portion 315 as opposed to
the five legs 216 in the first construction of the container 210.
Furthermore, as best shown in FIGS. 14 and 15, each leg 316 is located
more proximal to the central axis 311 compared with the radial spacing of
the feet 216 from the central axis 211, with the result that even less
material is required to form the legs 316 in the alternative embodiment
improved container 310. However, by having the legs 316 spaced more
proximal to the central axis 311, the standing ring of the container 310
is decreased, thereby increasing the likelihood of the container 310
toppling over by an applied force. Further, there is a disadvantage that,
being that the legs 316 are evenly spaced about the circumference, the
feet 321 are mirrored about the central axis 311, thereby creating the
possibility of the container 310 tilting about two opposing foot sections.
It will be appreciated by those skilled in the art that changes could be
made to the embodiments described above without departing from the broad
inventive concept thereof. It is understood, therefore, that this
invention is not limited to the particular embodiments disclosed, but it
is intended to cover modifications within the spirit and scope of the
present invention as defined by the appended claims.
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